A recently developed fastener assembly used to attach upholstery fabrics with loops on their back surfaces to foam seat cushions of the type used in automobiles includes a polymeric backing strip, a multiplicity of stems each secured at one end to and projecting from a first surface of the backing strip and having enlarged heads at their ends opposite the backing strip adapted to engage the loops on the upholstery material when the material is pressed against the heads, and an open porous permanent attachment layer attached to the surface of the backing strip opposite the stems. The fastener assembly is placed with its heads adjacent to the inner wall of a seat mold, a seat cushion is foamed in the mold, and the permanent attachment layer has sufficient open areas to afford movement of foam into it to permanently attach the fastener assembly to the newly foamed seat cushion.
This fastener assembly also typically includes a strip of steel sandwiched between the backing strip and the permanent attachment layer that provides means by which the fastener assembly can be magnetically held in a predetermined location against the inner wall of the mold in which the seat cushion is foamed. While the steel strip affords enough magnetic attraction to hold the strip in place prior to foaming, it presents a problem in a subsequent heat cure process during which the foam seat cushions removed from the mold are heated to about 125.degree. C. (250.degree. F.). This temperature causes longitudinal shrinkage in the polymeric backing strip, which shrinkage does not occur in the steel strip. Thus pieces of the thin steel strip either buckle within the fastener assembly giving it an uneven contour, or project from the ends of the fastener assembly and can cut the cushion, or the overlaying fabric, or even a person handling or sitting on the seat.
Additionally this fastener assembly has an elongate film layer overlying the heads and having longitudinal edge parts attached to the edges of the backing strip. This layer is positioned between the heads and the wall of the mold during the foaming process to prevent foam from moving into the spaces around the heads and stems which would reduce the ability of the heads to subsequently engage loops on the fabric. This film is adapted to then expose the heads during the heat cure process for the cushion by being meltable at a temperature below 125.degree. C. While such melting exposes the heads and stems, it also coats them with the film material which can detract from the holding ability of the heads.